Potentiometric investigation of the silver(I) complexes of a series of sulphur‐containing α,ω‐diamines

The composition and the stability constants of the complexes formed between Ag(I) and ligands of the type\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm NH}_2 ---({\rm CH}_2)_{\rm n} ---{\rm S---}({\rm CH}_2)_{\rm m} ---{\rm NH}_2, $$\end{document}where n,m = 2,2; 2,3; 2,4; 3,3; 3,4; 4,4, have been determined by a pH/pM‐metric method at 25°C in a 0.5 M (K)NO 3 medium. The determination of the stability constants proceeded by a combination of a graphical method and a least squares minimization procedure. The complex formation is discussed in comparison with silver complexes formed with S‐containing mono‐amines and in terms of the Taft σ*‐parameters for the substituents. Below pH = 4, the protonated complexes AgLH 2 3+ and AgL 2 H 4 5+ are formed and the thioethergroup is the only coordinating centre. In neutral and alkaline medium there was evidence for the species AgLH 2+ , Ag 2 L 2 H 2 4+ , Ag 2 L 2 H 3+ , Ag 2 L 2 2+ , AgL 2 H 3 4+ , AgL 2 H 2+ , AgL 2 + and Ag 2 L 2+ in which Ag + S and Ag + NH 2 bonds are involved. It is shown that in the Ag 2 L 2 2+ and Ag 2 L 2+ complexes the ligands effectively coordinate through all available donor centres.